The invention is related to the field of semiconductor fabrication and processing, and in particular to a technique to reduce dislocations in silicon wafers during growth of semiconductor materials, or during the processing of existing semiconductor materials.
Over 50% of solar cells produced today are manufactured from multicrystalline silicon (mc-Si) wafers. The electrical properties of the solar cell devices that are manufactured on mc-Si wafer substrates are extremely sensitive to the density of defects present in these materials. Defects inside the solar cell wafers, commonly referred to as “bulk defects” (e.g., impurities and structural defects), are particularly deleterious for solar cell efficiencies. The most damaging bulk defects are those that are most uniformly distributed, such as one-dimensional structural defects known as dislocations.
By decreasing the dislocation density of the multicrystalline silicon material without compromising bulk impurity concentrations, efficiency improvements of 10-40% relative may be achieved. Thus, the quality of multicrystalline silicon can be boosted to levels comparable to monocrystalline silicon, while retaining the cost advantage of multicrystalline silicon. This would enable multicrystalline silicon substrates, with minority carrier lifetimes approaching those of float zone material, to be incorporated into higher-efficiency device architectures.